Electronic tremulant device particularly for electronic organs



March 12, 1968 J. szABo ELECTRONIC TREMULANT DEVlCE PARTICULARLY FOR ELECTRONIC ORGANS 2 Sheets-Sheet 1 Filed Sept. 29, 1964 PPRENT LOC/ON AND DIRECT/ON OF MOVEMENT OF SOURCE TIME /N FIG. 2

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1 N VENTOR. JOH N SZABO PATENT AGENT United States Patent O 3,373,241 ELECTRONIC TREMULANT DEVICE PARTIC- ULARLY FOR ELECTRONIC ORGANS John Szabo, Kitchener, Ontario, Canada, assignor to Dominion Electrohome Industries Limited, Kitchener, Ontario, Canada Continuation-in-part of application Ser. No. 211,597, July 23, 1962. This application Sept. 29, 1964, Ser. No. 400,180

Claims. (Cl. 84-125) ABSTRACT OF THE DISCLOSURE A tremulant effect is created electronically by alternately and periodically increasing and decreasing the intensity of sound reproduced by one loudspeaker while at the same time alternately and periodically decreasing and increasing the intensity of the sound reproduced by another loudspeaker by supplying out of phase signals to the field coils of the loudspeakers, both loudspeakers each having a voice coil supplied with an electrical signal to be reproduced.

This is a continuation-in-part of application Ser. No. 211,597, filed July 23, 1962, now abandoned.

This invention relates to tremulant or vibrato sound effeet producing devices. More particularly, this invention relates to apparatus for producing tremulant sound effects by simulated movement of a sound source which preferably may be achieved either electrically or electrically and electromagnetically.

Generally speaking there have been two basic methods employed in the past to introduce periodic Variations of frequency and/or intensity in sound such as may be derived from electronic organs, for example, to produce certain enhancing tonal effects called vibrato or tremulant.

One method involves the utilization of some electronic means such as are shown in United States Patent Numbers 2,509,923, 2,973,681, 2,892,372 and 2,534,342 issued May 30, 1950, Mar. 7, 1961, June 30, 1959 and Dec. 19, 1950 respectively in the names of J. M. Hanert, C. L. Fender, H. G. Bauer and N. I. Daniel respectively.

The utilization of some such electronic means to impart Variations of frequency or phase to tones results in an effect known as vibrato and which is a simulation of the effect created by vibrating ones fingers on the strings of a violin or other stringed instrument. While vibrato is commonly used in connection with music produced by electronic Organs, it is seldom required in connection with true organ music.

A common method for producing tremulant effects involves the utilization of mechanical means to impart variations in the acoustical characteristics of the tone of music. EXamples of such prior art are United States Patent Numbers 2,995,054 and 2,780,302 issued Aug. 8, 1961 and Feb. 5, 1957 respectively in the names of D. J. Leslie and T. J. George respectively. General devices of the type exemplified by Patent No. 2,995,054, wherein a loudspeaker or loudspeakers are continnously revolved about an axis, are particularly popular. With such devices the movement of the sound source results in the following acoustical effects:

(1) Frequency and phase appear to periodically change at the point of observation due to the Doppler effect.

(2) The intensity of the sound appears to change due to the changing distance between the source and the observer.

(3) The continuous change in location of the sound source relative to the listener results in the simulation of the effect introduced by the change in relative location of organ pipes When successive notes are played.

All of the foregoing effects are pleasing and desirable in the production of organ music. However, the revolving speaker system has a number of disadvantages due to its mechanical limitations. For example, the foregoing effects are limited by the relatively small distance between the two extreme positions of the source. In order to olfset this disadvantage, the size and mass of the unit can be increased, but there are obvious practical limitations to increasing the size and mass of the unit. In a practical system employing revolving speakers the physical size and weight of the apparatus are quite substantial. This raises problems of dynamic balance because of the mass involved. Other problems include inherent noise due to the revolving of the speakers, and wearing of bushings, electrical brushes and collector rings necessitating servicing thereof. An additional disadvantage of such a system is the time taken to start the system in operation and to stop the system due to the inertia of the mass involved. Systems employing rotatable deflectors, e.g. the system disclosed in United States Patent No. 2,869,667 issued Jan. 29, 1959 (D. J. Leslie), suffer similar disadvantages.

Accordingly it is a primary object of my invention to produce tremulant eifects by simulating the movement of a sound source with respect to an Observer, rather than by actually moving the sound source with respect to the Observer, as has been the case in the prior art.

It is another object of my invention to provide such apparatus as aforementioned wherein the separation of the two extreme positions o-f the apparent moving source is not limited, Which results in greater apparent Variations of frequency, phase and amplitude than are practical with apparatus employing an actual moving source.

In apparatus embodying my invention preferably no mechanical moving parts are employed. Hence, there is no wear or mechanical servicing required, and, also, there is no noise such as may be attributed to a revolving speaker or deflector system. Furthermore, because no mechanical moving parts are necessary, all problems of dynamic balancing are eliminated, In addition, with preferred apparatus embodying my invention it is possible to obtain instant starting and Stopping of tremulant effects.

Preferred apparatus embodying my invention employs a simple electronic circuit, Which is not costly in nature, for control of the tremulant effect, and the period of the treniulant effect may be simply and readily varied.

In brief, in accordance with one embodiment of this invention there is provided apparatus for producing a tremulant sound effect Which comprises at least first and second sound reproducing devices which are adapted to reproduce sounds from electrical signals. The sound reproducing devices are physically spaced apart from each other. Means are provided for supplying an electrical signal to the sound reproducing devices. These laSt-mentioned means include control means for alternately and periodically increasing and decreasing the amplitude of the electrical signal supplied to one of the sound reproducing devices over a time interval within the sound retention ability of the human ear while alternately and periodically decreasing and increasing respectively the amplitude of the electrical signal supplied to the other of the sound reproducing devices, also over a time interval Within the sound retention ability of the human ear.

My invention will become more apparent from the following detailed disclosure taken in conjunction with the appended drawings in which:

FIGURE 1 illustrates two sound sources spaced apart from each other and an observer;

FIGURE 2 is a graph showing the relative sound output levels of the two sources in FIGURE 1 and their combined outputs;

3 FIGURE 3 is a chart showing the apparent location and direction of movement of the apparent sound source relative to an Observer;

FIGURE 4 shows preferred apparatus embodying my invention; and

FIGURES 5-7 inclusive illustrate alternative embodiments of my invention.

From the following detailed description it will be seen that it is not necessary to impart actual movement to a source of sound in order to derive sound effects similar to those created by actual movement of a sound source. In addition, it will be seen that all the effects such as changes in frequency, phase and amplitude which can be produced by actual movement of a sound source also can be produced by only simulating the movement of a sound source. Referring specifically to FIGURE 1, there are shown two sound sources and 11, each of which are stationary, and which are spaced apart from each other at a fixed distance. An Observer or listener is located at point 12. The acoustical output from sound source 10 is shown in FIGURE 2 at 10a, whereas the acoustical output of sound source 11 is shown at FIGURE 2 at 11a. It should be n-oted that the acoustical outputs of sound sources 10 and 11 are periodic in nature, in phase and continually change in magnitude or intensity at an equal rate with time but opposite in sign, as shown in FIGURE 2. In other words, while the intensity of the sound reproduced by one of the sound reproducing devices is alternately and periodically increasing and decreasing, the intensity of the sound reproduced by the other of the sound reproducing devices is alternately and periodically decreasing and increasing respectively. The curve numbered 13 in FIGURE 2 represents the combined acoustical output of sound sources 10 and 11. While the acoustical outputs of sound sources 10 and 11 have been shown, for the sake of simplicity, to be in phase in FIGURE 2, this is not essential for the production of tremulant effects.

Insofar as concerns the Observer located at point 12 in FIGURE 1, it will be seen from reference to FIGURE 2 that at time 1 of FIGURE 2 the observer will find that the sound originates from source 11. At time 3 in FIG- URE 2 the Observer at point 12 will find that the sound originates from sound source 10. The Observer at point 12 also will find that the source of sound alternately and periodically originates from either sound source at every second interval of time. From the table shown in FIGURE 3, it will be seen that at intermediate time intervals 0, 2, 4, etc., the sound will appear to originate at a point halfway between the two fixed sound sources 10 and 11, in other words from point 14. In fact, during intermediate time intervals the sound Will always appear to originate from one point on the line 15 connecting sound sources 10 and 11 and not from both sources. Furthermore, the apparent single source will appear to be periodically moving from sound source 11 to sound source 10 during the time interval from 1 to 3 in FIGURE 2 and from sound source 10 to sound source 11 during the time interval 3 to 5 in FIGURE 2. The apparent single sound source will continue to move periodically as afore-mentioned as long as the output levels of sound sources 10 and 11 continue to change in accordance with FIGURE 2. In addition to the apparent movement of a single source created by the periodically changing outputs of the two fixed sound sources, the Observer will also detect a shift in frequency and phase in the tone, just as if the sound were produced by an actual moving source in place of the two fixed sources. If the Observer were to move closer to one source than to the other, he would also detect a periodic change in the level of the sound as the apparent source moved back and forth relative to him. Thus, it will be seen from the foregoing that two fixed sound sources can be ernployed to create the tremulant effect produced by a moving sound source. It must be clearly understood, however, that since tremulant is an audible eflfect audibly detected by the Observer, it is essential to its production that the period of the change in intensity of the sound waves from sound sources 10 and 11, eg. the time interval between 1 and 5 for the envelope of wave lila in FIGURE 2, must be within the sound retention -ability of the human ear. Consequenlty, where this change is effected by varying the amplitude of the electrical signal supplied to the sound sources, the period of this variation must be over a time interval within the sound retention ability of the human ear. From a practical point of view the time interval for a complete period should be milliseconds (10 c.p.s.) or greater, from 100 milliseconds to 1 second (1 c.p.s.) being preferred. Best results may be achieved at about milliseconds (approximately 6.7 c.p.s.) in many cases.

Turning now to FIGURE 4, I have shown preferred apparatus embodying my invention. This apparatus comprises two electro-dynamic speakers 10 and 11 each having a voice coil 15 and 15 respectively, each having field coils 17 and 18 respectively and each having iron cores 1'7a and 18a respectively. An electrical signal is supplied to voice coils 15 and 16 through an amplifier 19 having input and output terminals 20 and 21 respectively, the latter of which are electrically connected with voice coils 15 and 15 through conductors 22. Control means 23 in the form of a multi-vibrator are provided for alternately and periodically increasing and decreasing the intensity of the sound reproduced by one of speakers 10 and 11, while alternately and periodically decreasing and increasing respectively the sound reproduced by the Other of the loudspeakers, all within the sound retention ability of the human ear. The multi-vibrator is conventional in nature and comprises two electron discharge devices 24 and 25, resistors R1, R2 and R3 and capacitors Cl, G2 and G3, all connected as shown in FIGURE 4. The multivibrator has two output terminals 26 and 27, each output terminal being connected through a field coil to a source of positive potential E+. It will be seen that resistor RB is a Variable resistor, and the setting of this resistor may be altered to vary the period of switching of the multi-vibrator over a range so that the intensity of the sound from the loudspeakers is varied over a time interval within the sound retention ability of the human ear.

In the operation of the embodiment Of my invention shown in FIGURE 4, an electrical signal is supplied to voice coils 15 and 16 through amplifier 19 and conductors 22. As the multi-vibrator switches, field coils 17 and 18 are alternately and periodically energized and de-energized, e.g. between 1 and 10 c.p.s., so as to alternately and periodically increase and decrease the intensity of the sound reproduced by speaker 10, while alternately and periodically decreasing and increasing respectively the intensity of the sound reproduced by loudspeaker 11, which, in the aforernentioned manner and when the period is within the sound retention ability of the human ear, creates the effect of an apparent moving source, which, in turn, results in tremulant effects.

The embodiment of my invention shown in FIGURE 5 is similar to that shown in FIGURE 4 and also is a preferred embodiment. In this embodiment the multi-vibrator of FIGURE 4 is replaced with a sine Wave oscillator 60, a phase inverter 61 and a push-pull Output stage 62. The sine wave oscillator may oscillate at a frequency between 1 and 10 c.p.s. to produce the tremulant effect. With such a system field coils 17 and 18 are alternately and periodically energized and de-energized as in the case of the system shown in FIGURE 4 and described hereinbefore.

It will be noted that the systems of FIGURES 4 and 5 operate electrically and electromagnetically.

In the embodiment of my invention shown in FIGURE 6, two amplifiers 1911 and 1% are provided each having Output terminals 21a, 21b respectively and input terminals 20a and 20b respectively. Output terminals 21a and 21b are electrically connected to speakers 10 and 11 respectively. Two potentiometers 36 and 37 each having a movable contact 36a and 3711 respectively are provided, and an input signal is supplied to potentiometers 36 and 37 through conductors 38. The movable contacts 36a and 37a are connected to input terminals 20a and 2012 respectively. Any suitable means (not shown) are provided connecting movable contacts 36a and 37a together in such a manner that the movable contacts are movable periodically, e.g. between 1 and c.p.s., so as to alternately and periodically increase and decrease the voltage at one of the movable contacts, while alternately and periodically decreasing and increasing respectively the voltage at the other of the movable contacts, so as to alternately and periodically increase and decrease the amplitude of the electrical signal supplied to loudspeaker 10, while alternately and periodically decreasing and increasing respectively the amplitude of the electrical signal supplied to loudspeaker 11 to create an apparent moving sound source and resultant tremulant effects. Of course, the inputs of amplifiers l9a and 19b can be controlled by any suitable electronic or electromechanical means, the latter being either resistive, inductive or capacitive.

The embodiment of my invention shown in FIGURE 7 comprises an amplifier 19 having input and output terminals 20 and 21 respectively, and a transformer having two primary windings 39 and 40 and two secondary windings 41 and 42. The transformer also has a rotatable iron core 43 which may be rotated about an axis 44 by any suitable means (not shown). Secondary winding 41 is electrically connected to speaker 10, while secondary winding 42 is electrically connected to speaker 11. An electrical signal is applied to input terminals 20, amplified by amplifier 19 and is supplied in phase to primary windings 39 and 40. In the position of core 43 shown in FIGURES 7 there is maximum coupling between 'primary winding 40 and secondary winding 41 and minimum coupling between the primary Wnding 39 and secondary winding 42. Consequently, the magnitude of the electrical signal supplied to loudspeaker 10 is considerably greater than the magnitude of the electrical signal supplied to loudspeaker 11, this being reversed when rotatable core 43 is rotated 90 from the position shown in FIGURE 7. Thus, it will be seen that during rotation of core 43, e.g. between 1 and 10 c.p.s., the magnitude of the electrical signal supplied to speaker 10 alternately and periodically increases and decreases in intensity, while the magnitude of the electrical signal supplied to speaker 11 alternately and periodically decreases and increases in intensity, thereby creating the effect of an apparent moving source and consequent tremulant effects. Of course, control over the coupling of the transformers may be effected in other Ways. For example, transformers with Variable gaps may be employed.

While I have disclosed certain preferred embodiments of my invention, those skilled in the art will appreciate that changes and modifications may be made therein without departing from the spirit and scope of my invention as defined in the appended claims.

What I claim as my invention is:

1. Apparatus for producing a tremulant sound effect which comprises first and second loudspeakers each having a field coil and a voice coil, said loudspeakers being physically spaced apart from each other and being adapted to reproduce sounds from electrical signals supplied to said voice coils, means for supplying an electrical signal to said voice coils, and control means electrically and electromagnetically alternately and periodically increasing and decreasing the intensity of the sound reproduced by one of said loudspeakers over an interval within the sound retenton ability of the human ear while electrically and electromagnetically alternately periodically decreasing and increasing respectively the intensity of the sound reproduced by the other of said loudspeakers over an interval within the sound retention ability of the human ear, thereby to produce a tremulant sound effect, said control means comprising means for supplying electrical signals out of phase with respect to each other to said field coils.

2. Apparatus according to claim 1 wherein said intervals each are greater than milliseconds.

3. Apparatus according to claim 2 wherein said intervals each are between 100 milliseconds and 1 second.

4. Apparatus according to claim 1 wherein said control means include a multivibrator.

5. Apparatus according to claim 1 wherein said control means include a multivibrator and means for adjusting the period of said multivibrator.

6. Apparatus according to claim 1 wherein said control means include a multivibrator, said multivibrator having two output terminals each connected to a different one of said field coils.

7. Apparatus according to claim 6 wherein said means for supplying said electrical signal to said first and second loudspeakers include an amplifier having input and output terminals, and means electrically connecting said output terminal and said voice coils.

8. Apparatus according to claim 7 further including means for adjusting the period of said multivibrator.

9. Apparatus according to claim 1 wherein said control means include a sine wave oscillator, a phase inverter and a push-pull output stage, said sine wave oscillator supplying an output signal therefrom to said phase inverter, said phase inverter supplying an output signal therefrom to said push-pull output stage.

10. Apparatus according to claim 9 wherein said pushpull output stage has two output terminals each connected to a different one of said field coils.

References Cited UNITED STATES PATENTS 2,ll4,680 4/1938 Goldsmith 84-125 3,049,040 8/1962 Leslie 84-125 X 3,255,297 6/1966 Long 84-125 X 3,267,l96 8/1966 Welsh et al. 84-125 X JOHN S. HEYMAN, Primary Examiner. ARTHUR GAUSS, Examner. D. D. FQRRER, Assistant E :amr'ner 

